The present invention relates to separation and purification of hydrogen gas from a fluid mixture and, more particularly, to a membrane composition operative as a hydride battery component.
A common technology for extracting high purity hydrogen from industrial gas streams involves selectively diffusing hydrogen through a membrane. High purity hydrogen is used extensively in semiconductor manufacture, fuel cell operation and hydrogenation reactions. Membranes capable of selectively passing hydrogen therethrough have utilized palladium or palladium alloys alone, or supported structurally by a matrix. A suitable hydrogen purification membrane requires a thick enough palladium layer to be made which is free of holes and structurally sound over a working lifetime of at least several months. A palladium-silver membrane is typical of those currently in use. Palladium-silver membranes are limited in their utility due to material costs and limited throughput associated with relatively high resistance to hydrogen permeation. Alternative membrane materials which have been considered as substitutes for palladium-silver have included palladium coated vanadium, niobium, tantalum, and vanadium-nickel. The palladium coat on such membranes functions to increase hydrogen permeation at temperatures below 700xc2x0 C. and further, to protect the underlying substrate of vanadium, niobium, tantalum or vanadium-nickel from corrosion associated with impurities in the input gas stream. A limitation associated with palladium coated alloys currently under development to supplant palladium-silver is embrittlement upon contact with hydrogen at room temperature. Membrane embrittlement occurs when a membrane unit is rapidly cooled from operating temperature to room temperature. Rapid cooling is associated with power disruption, membrane unit failure, an emergency override situation and the like. Thus, there exists a need to find hydrogen permeable alloys that are more embrittlement resistant than palladium coated vanadium, niobium, tantalum or vanadium-nickel.
A number of technologies benefit from coating palladium onto surfaces in addition to hydrogen separation. In particular, hydride battery electrodes and bracheotherapy are improved by the present invention.
A hydride battery electrode is coated with palladium or a palladium alloy to improve hydride storage properties and recycle characteristics.
A hydrogen purification membrane including a metallic substrate likewise has improved properties upon coating with palladium and a surface species of an alkali metal, alkaline earth element or alkaline earth cation.
Novel metal hydrogen purification membranes include vanadium alloyed with at least 1 to 20 atomic percent nickel and/or 1 to 20 atomic percent cobalt and/or 1 to 20 atomic percent palladium.